1. Field of the Invention
The invention relates to a communications system which has a ring-shaped network.
2. Description of the Related Art
Digital, computer-controlled switching equipment are predominantly utilized in private communications systems. The central control means can be a microprocessor system for small through medium switching equipments which have about 10-500 subscriber lines. The central control device usually communicates directly with a switching matrix network and, so as to relieve the central control, communicates with a plurality of subscriber line equipment by way of one or more communications sub-controllers. The subscriber equipments are connected to the subscriber line equipment which are mounted in specific acceptance means, and the connection is made via central office lines using suitable transmission procedures. In the subscriber line equipment, the signalling to the subscriber equipment as well as to the central control is accomplished using suitable hardware or, respectively, software or, respectively, procedures. For this purpose, the subscriber line equipment collects the signalling information which is received from the subscriber equipment and communicates it for further processing to the central control means after suitable editing. The communication in the opposite transmission direction occurs in a similar manner. The central control essentially executes the switching-oriented jobs, for example, identification of the switching matrix network setting on the basis of the called subscribers number. The switching equipment and the system components in the subscriber line region are operated and monitored with an operating terminal that communicates with the switching equipment and essentially with the controllers of the switching equipment by way of a specific port or a subscriber line. Such operating or, respectively, monitoring functions, for example, are modification of subscriber-associated data in the data base, the loading of the memories of the implemented processor systems with semi-permanent or, respectively, permanent data upon occurrence of down system components or for updating. The indication of faults at the operating terminal and the automatic start of fault localizing and analysis procedures can also be accomplished.
For some time, what are referred to as "local area networks" have been utilized to an increasing degree in addition to the traditional private branch exchange networks. These local networks usually represent independent communications networks; for example, a plurality of terminals which communicate with one another as well as with a central computer means. With increasing transmission rates of information, more and more ring-shaped local networks are being utilized. In contrast to bus networks, a point-to-point connection is made between the individual subscriber equipments. This means that the transmission media, for example, light waveguide transmission systems, can be utilized through which information can be transmitted with extremely high transmission rates, for example, 100Mbit/s. In order to adapt to the conditions of subscriber equipment that transmit pack-oriented and line-switching-oriented, a division of the transmission capacity of a ring-shaped network is also being used. Thus, for example, a line-switching region can be defined in which a specific sub-capacity, for example, 64Kbit/s, is allocated to a line-switching subscriber for the duration of a connection. Also, a packet region can be defined for packet-transmitting subscribers. These allocations are, respectively stored in a memory or, respectively, a register which is provided therefore in a ring access means which executes access onto the ring-shaped network.
For the connection of additional subscriber equipment to a private switching equipment that is to be locally stationed in the region of a ring-shaped network, it is desirable to use the ring-shaped network as an offering network, whereby the private switching equipment is then to be connected to the ring-shaped network.
Reference may be made to U.S. Pat. No. 4,661,952 and to the publication by Siemens entitled "ISDN in the Office" a special issue of Telcom Report and Siemens Magazine Com. These publications are hereby incorporated by reference.